Wireless ic device component and wireless ic device

ABSTRACT

A wireless IC device includes a wireless IC chip, a coupling electrode, and a radiation plate. The coupling electrode includes coupling portions arranged to be coupled to the wireless IC chip and a pair of opposing ends. The pair of opposing ends are capacitively coupled to each other and oppose the radiation plate to be coupled to the radiation plate. The wireless IC chip uses the radiation plate as an antenna to transmit and receive signals having certain frequencies to and from an RFID system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless integrated circuit (IC) devicecomponents and wireless IC devices. More particularly, the presentinvention relates to a wireless IC device component and a wireless ICdevice preferably for use in a Radio Frequency Identification (RFID)system.

2. Description of the Related Art

Hitherto, RFID systems have been developed as article managementsystems. In such an RFID system, a reader-writer producing an inductionelectromagnetic-field communicates with an IC chip (also referred to asan IC tag or a wireless IC chip) in a non-contact manner. The IC chip isattached to, for example, an article or a container and stores certaininformation to be transmitted. The IC chip is coupled to an antenna,that is, a radiation plate to enable communication with thereader-writer.

Japanese Registered Utility Model No. 3148168 discloses a wireless ICdevice which includes a wireless IC, an annular electrode including apair of ends, and a matching portion provided on the pair of ends of theannular electrode and in which a dipole radiation plate is connected toa current maximum point of the annular electrode. In the wireless ICdevice, the wireless IC is coupled to the matching portion and theannular electrode is electromagnetically coupled to the radiation plate.The wireless IC is coupled to the radiation plate via the annularelectrode.

In the wireless IC device described above, the use of the annularelectrode (coupling electrode) enables the mounting accuracy of thewireless IC to be reduced so as to improve the radiationcharacteristics. However, such an annular electrode (coupling electrode)has an inductive reactance complementing the impedance and there is aproblem in that a long electrical length increases the value of theinductive reactance so as to deteriorate impedance matching between thewireless IC and the radiation plate.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of thepresent invention provide a wireless IC device component and a wirelessIC device that are capable of increasing the electrical length of acoupling electrode and achieving satisfactory impedance matching betweena wireless IC and a radiation plate to more satisfactorily couple thecoupling electrode to the radiation plate.

A wireless IC device component according to a first preferred embodimentof the present invention preferably includes a wireless IC, and acoupling electrode including at least one coupling portion to be coupledto the wireless IC directly or via a feed circuit and a pair of endsthat are capacitively coupled to each other.

A wireless IC device of a second preferred embodiment of the presentinvention preferably includes a wireless IC, a coupling electrodeincluding at least one coupling portion to be coupled to the wireless ICdirectly or via a feed circuit and a pair of ends that are capacitivelycoupled to each other, and a radiation plate coupled to the couplingelectrode.

A wireless IC device of a third preferred embodiment of the presentinvention preferably includes a wireless IC, a coupling electrodeincluding at least one coupling portion to be coupled to the wireless ICdirectly or via a feed circuit and a pair of opposing ends defined by acutout of the coupling electrode, and a radiation plate that is opposedto the opposing ends in the coupling electrode so as to be capacitivelycoupled to the opposing ends.

In the wireless IC device component of the first preferred embodimentand the wireless IC device of the second preferred embodiment, thecoupling electrode is preferably defined by an annular electrode via thepair of ends that are capacitively coupled to each other. The couplingelectrode has an inductive reactance (XL: jωL) caused by the electricallength and a capacitive reactance (XC: 1/jωC) caused by the pair of endsthat are capacitively coupled to each other. Since the inductivereactance has a phase opposite to that of the capacitive reactance, theimpedance does not significantly increase because of the increase in theelectrical length of the coupling electrode. In other words, it ispossible to achieve the impedance matching between the wireless IC andthe radiation plate even if the electrical length of the couplingelectrode is increased. Specifically, since the paired ends in thecoupling electrode are capacitively coupled to each other to provide thecapacitive reactance, it is necessary for the coupling electrode to havean increased inductive reactance in order to achieve certain impedanceand the electrical length of the coupling electrode is increased. Theincreased electrical length causes the coupling electrode to receive anincreased amount of magnetic field from the radiation plate and, thus,the magnetic coupling between the coupling electrode and the radiationplate is further strengthened.

In the wireless IC device of the third preferred embodiment, thecapacitive and magnetic coupling between the coupling electrode and theradiation plate causes the wireless IC to be coupled to the radiationplate so as to establish communication between the wireless IC and anRFID system in a non-contact manner. The coupling electrode has aninductive reactance (XL: jωL) caused by the electrical length and acapacitive reactance (XC: 1/jωC) caused by the coupling electrode andthe radiation plate. Since the inductive reactance has a phase oppositeto that of the capacitive reactance, the impedance does notsignificantly increase because of the increase in the electrical lengthof the coupling electrode. In other words, it is possible to achieve theimpedance matching between the wireless IC and the radiation plate evenif the electrical length of the coupling electrode is increased.Specifically, since the coupling electrode is capacitively coupled tothe radiation plate to provide the capacitive reactance, it is necessaryfor the coupling electrode to have an increased inductive reactance inorder to achieve certain impedance and the electrical length of thecoupling electrode is increased. The increased electrical length causesthe coupling electrode to receive an increased amount of magnetic fieldfrom the radiation plate and, thus, the magnetic coupling between thecoupling electrode and the radiation plate is further strengthened.

When the wireless IC is a chip type wireless IC and is directly coupledto the coupling electrode, for example, the coupling electrodepreferably performs the impedance matching between the wireless IC chipand the radiation plate. The wireless IC may be indirectly coupled tothe coupling electrode via a feed circuit board including a feedcircuit, i.e., a resonant circuit and/or a matching circuit. In thiscase, the feed circuit preferably performs the impedance matching withthe wireless IC and the coupling electrode preferably performs theimpedance matching between the feed circuit and the radiation plate.

When the coupling electrode is capacitively coupled to the radiationplate via the opposing ends, the mounting accuracy of the couplingelectrode in the wireless IC on the radiation plate is not strictlylimited. The same applies to the case in which the wireless IC ismounted on the feed circuit board.

In addition, the frequency of a signal used in the communication with areader-writer is substantially determined by the feed circuit includingthe resonant circuit and/or the matching circuit which have a certainresonant frequency. The feed circuit is preferably designed inaccordance with the impedances of the wireless IC and the radiationplate to be used to adapt to various impedances and to broaden thefrequency band in which the impedance matching is enabled. Furthermore,arranging the coupling electrode so that the coupling electrode iscoupled to the feed circuit and the radiation plate enables a signal tobe efficiently transmitted from the radiation plate via the couplingelectrode, so as to improve the radiation characteristics of the signal.

According to various preferred embodiments of the present invention, itis possible to increase the electrical length of the coupling electrodeand to achieve satisfactory impedance matching between the wireless ICand the radiation plate. As a result, it is possible to moresatisfactorily couple the coupling electrode to the radiation plate.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a wireless IC device according to afirst preferred embodiment of the present invention.

FIG. 2 schematically illustrates an example of electromagnetic-fielddistribution in the wireless IC device.

FIGS. 3A and 3B are diagrams showing a wireless IC device componentaccording to a second preferred embodiment of the present invention,where FIG. 3A is a front view and FIG. 3B is a perspective view.

FIG. 4 is a perspective view showing a wireless IC device componentaccording to a third preferred embodiment of the present invention.

FIGS. 5A and 5B are diagrams showing a wireless IC device according to afourth preferred embodiment of the present invention, where FIG. 5A is aplan view and FIG. 5B is an exploded perspective view.

FIG. 6 is a cross-sectional view showing the main portion of thewireless IC device according to the fourth preferred embodiment of thepresent invention.

FIG. 7 is a plan view showing a modification of a coupling electrodeaccording to a preferred embodiment of the present invention.

FIG. 8 is an elevation view showing another arrangement of the couplingelectrode on a radiation plate.

FIGS. 9A and 9B are diagrams showing a coupling electrode of a wirelessIC device according to a fifth preferred embodiment of the presentinvention, where FIG. 9A is a plan view showing a state in which a feedcircuit board is installed and FIG. 9B is a plan view showing a state inwhich the feed circuit board is removed.

FIG. 10 is an equivalent circuit showing a feed circuit in the wirelessIC device according to the fifth preferred embodiment of the presentinvention.

FIG. 11 is a perspective view showing a state in which a wireless ICchip is installed on the feed circuit board included in the wireless ICdevice according to the fifth preferred embodiment of the presentinvention.

FIG. 12 includes plan views showing a layered structure of the feedcircuit board.

FIG. 13 is a perspective view of an example in which the couplingelectrode is provided on the feed circuit board.

FIG. 14 is a perspective view schematically showing the structure of awireless IC device according to a sixth preferred embodiment of thepresent invention.

FIG. 15 is a perspective view showing the wireless IC device accordingto the sixth preferred embodiment of the present invention.

FIG. 16 is a cross-sectional view showing a modification of the wirelessIC device according to a preferred embodiment of the present invention.

FIGS. 17A and 17B are diagrams showing a wireless IC device componentaccording to a seventh preferred embodiment of the present invention,where FIG. 17A is a perspective view and FIG. 17B is a developed view ofa coupling electrode.

FIG. 18 is a perspective view showing a wireless IC device componentaccording to an eighth preferred embodiment of the present invention.

FIGS. 19A and 19B are diagrams showing a wireless IC device componentaccording to a ninth preferred embodiment of the present invention,where FIG. 19A is a cross-sectional view and FIG. 19B is a perspectiveview of a coupling electrode.

FIG. 20 is a cross-sectional view showing a wireless IC device componentaccording to a tenth preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a wireless IC device component and a wirelessIC device according to the present invention will be described withreference to the attached drawings. In the description, the wireless ICdevice preferably includes a radiation plate and the wireless IC devicecomponent is defined as the wireless IC device with the radiation platebeing omitted. The radiation plate is preferably provided at the side ofan article and the wireless IC device component is coupled to theradiation plate to define the wireless IC device. The same referencenumerals are used in the drawings to identify the same or substantiallythe same components and portions. A duplicated description of suchcomponents and portions is omitted herein.

First Preferred Embodiment

A wireless IC device according to a first preferred embodiment of thepresent invention preferably includes a wireless IC chip 5 arranged toprocess transmission and reception signals having certain frequencies, aradiation plate 115 provided on a base 110, such as a polyethyleneterephthalate (PET) film, for example, and a coupling electrode 125provided on a base (not shown), such as a PET film, for example, asshown in FIG. 1.

The coupling electrode 125 preferably includes a pair of couplingportions 126 a and 126 b to be coupled to the wireless IC chip 5 and apair of opposing ends 126 c and 126 d defined by a cutout of thecoupling electrode 125. The wireless IC chip 5 preferably includes, forexample, a clock circuit, a logic circuit, and a memory circuit.Necessary information is stored in the wireless IC chip 5. A pair ofinput-output terminal electrodes (not shown) is provided on the rearsurface of the wireless IC chip 5. The pair of input-output terminalelectrodes is mounted on the pair of coupling portions 126 a and 126 bof the coupling electrode 125 via a conductive adhesive or othersuitable adhesive, for example.

The radiation plate 115 preferably includes, for example, a metallaminate made of a conductive material, such as an aluminum foil or acopper foil, that is provided on substantially the entire surface of thebase 110. The coupling electrode 125 is preferably arranged so as to besubstantially perpendicular to the radiation plate 115 with the opposingends 126 c and 126 d being opposed to the radiation plate 115. Theopposing end 126 c is opposed to the opposing end 126 d so as to becapacitively coupled to the opposing end 126 d, so that the couplingelectrode 125 electrically forms an annular electrode. A lower-sideportion of the coupling electrode 125 including the opposing ends 126 cand 126 d is capacitively and magnetically coupled to the radiationplate 115. The radiation plate 115 may preferably be provided as aportion of an article, for example, without being combined with thecoupling electrode 125 in advance.

Preferably, the coupling electrode 125 has a certain length from thecoupling portions 126 a and 126 b to the opposing ends 126 c and 126 d,has a certain resonant frequency corresponding to the electrical length,and also functions as a matching portion arranged to perform phasematching. In addition, the coupling electrode 125 performs impedancematching between the wireless IC chip 5 and the radiation plate 115.

A transmission signal that is sent from the wireless IC chip 5 and thathas a certain frequency is transmitted to the radiation plate 115 viathe coupling electrode 125, and a signal having a certain frequency isselected by the coupling electrode 125 from signals received by theradiation plate 115 and the selected signal is supplied to the wirelessIC chip 5. Accordingly, in the wireless IC device, the wireless IC chip5 is operated with the signal received by the radiation plate 115 andthe response signal from the wireless IC chip 5 is externally radiatedfrom the radiation plate 115.

In the wireless IC device, the capacitive and magnetic coupling betweenthe coupling electrode 125 and the radiation plate 115 causes thewireless IC chip 5 to be coupled to the radiation plate 115 so as toestablish communication between the wireless IC chip 5 and an RFIDsystem in a non-contact manner. Energy is transmitted between thecoupling electrode 125 and the radiation plate 115 primarily through themagnetic coupling.

In the wireless IC device, the opposing ends 126 c and 126 d of thecoupling electrode 125 are opposed to the radiation plate so as to becapacitively coupled to the radiation plate. Such capacitive couplingcauses the opposing ends 126 c and 126 d of the coupling electrode 125to be electrically connected to each other via the radiation plate 115to electrically form an annular electrode.

The coupling electrode 125 has an inductive reactance (XL: jωL) causedby the electrical length and a capacitive reactance (XC: 1/jωC) causedby the coupling electrode 125 and the radiation plate 115. Since theinductive reactance has a phase opposite to that of the capacitivereactance, the impedance does not significantly increase because of theincrease in the electrical length of the coupling electrode 125. Inother words, it is possible to achieve the impedance matching betweenthe wireless IC chip 5 and the radiation plate 115 even if theelectrical length of the coupling electrode 125 is increased. Thus, theelectrical length of the coupling electrode 125 can be increased tostrengthen the magnetic coupling between the coupling electrode 125 andthe radiation plate 115.

In the first preferred embodiment, the coupling electrode 125 ispreferably arranged such that a loop surface of the coupling electrode125, that is, a surface of the coupling electrode 125 on which thewireless IC chip 5 is disposed, is perpendicular or substantiallyperpendicular to the radiation plate 115 so as to produce a magneticfield parallel to the radiation plate 115. Consequently, an electricfield perpendicular or substantially perpendicular to the radiationplate 115 is produced, a magnetic field is induced by the electric-fieldloop, and this chain expands the electromagnetic-field distribution. Asa result, the wireless IC device is functional even if the wireless ICdevice is arranged on the metal surface. In addition, it is alsopossible to cause the metal surface to function as the radiation plate.

FIG. 2 schematically illustrates an example of the electromagnetic-fielddistribution produced by the coupling electrode 125 (magnetic fields Hare indicated by broken lines and electric fields E are indicated byfine lines). The annular coupling electrode 125 functions as amagnetic-field antenna. The coupling electrode 125 causes the magneticfields H to induce the electric fields E perpendicular or substantiallyperpendicular to the radiation plate 115, the electric fields E inducethe magnetic fields H, and this chain expands the electromagnetic-fielddistribution. Although the coupling electrode 125 is described as thetransmission antenna, the coupling electrode 125 similarly operates as areception antenna due to the reversibility of the antenna. Morespecifically, an electromagnetic field induces a magnetic field H, themagnetic field H induces an electric field E perpendicular orsubstantially perpendicular to the surface of the radiation plate 115,and the electric field E produce a magnetic field H parallel orsubstantially parallel to the surface of the radiation plate 115, whichare coupled to the coupling electrode 125.

The wireless IC device component is functional even if a component onwhich the wireless IC device component is mounted is made of a metal,and the wireless IC device component similarly operates even if acomponent on which the wireless IC device component is mounted is anarticle made of a material other than metal, for example, an electrolytesuch as blood, soybean paste, saline solution, or soapy water. When thearticle on which the wireless IC device component is mounted is a metalor an electrolyte, transmission and reception may be performed from asurface opposite to the surface on which the wireless IC devicecomponent is installed because a current passes through the surfaces ofthe article.

The wireless IC device can preferably use, for example, frequencieswithin an ultra high frequency (UHF) band (850 MHz to 970 MHz).

As described above, since the resonant frequency of a signal is set bythe coupling electrode 125 in the wireless IC device of the firstpreferred embodiment, the wireless IC device operates as it is even ifthe wireless IC device is mounted on various articles. Accordingly,variations in the radiation characteristics are prevented or minimizedand it is not necessary to change the design of, for example, theradiation plate 115 for each article upon which the wireless IC deviceis to be mounted. The frequency of a transmission signal radiated fromthe radiation plate 115 and the frequency of a reception signal to besupplied to the wireless IC chip 5 substantially correspond to theresonant frequency of the coupling electrode 125. Since the frequenciesof the transmission and reception signals are determined in the couplingelectrode 125, the frequency characteristics do not vary such thatstable frequency characteristics are achieved, regardless of the shape,the size, and/or the arrangement relationship of the radiation plate115, for example, even if the wireless IC device is rounded or issandwiched between dielectric materials.

Second Preferred Embodiment

A wireless IC device component according to a second preferredembodiment of the present invention preferably includes a couplingelectrode 135, as shown in FIGS. 3A and 3B. The coupling electrode 135preferably includes a pair of coupling portions 136 a and 136 b arrangedto be coupled to the wireless IC chip 5 and a pair of opposing ends 136c and 136 d. The opposing ends 136 c and 136 d are capacitively coupledto each other.

The opposing end 136 c is capacitively coupled to the opposing end 136d, so that the coupling electrode 135 electrically forms an annularelectrode and functions as a magnetic-field antenna. The wireless ICdevice component functions as a wireless IC device with the couplingelectrode 135 being coupled to the radiation plate 115, similarly to thecoupling electrode 125 shown in the first preferred embodiment.

The coupling electrode 135 has an inductive reactance (XL: jωL) causedby the electrical length and a capacitive reactance (XC: 1/jωC) causedby the paired opposing ends 136 c and 136 d that are capacitivelycoupled to each other. Since the inductive reactance has a phaseopposite to that of the capacitive reactance, the impedance does notsignificantly increase because of the increase in the electrical lengthof the coupling electrode 135. In other words, it is possible to achievethe impedance matching between the wireless IC chip 5 and the radiationplate 115 even if the electrical length of the coupling electrode 135 isincreased. Thus, the electrical length of the coupling electrode 135 maybe increased to strengthen the magnetic coupling between the couplingelectrode 135 and the radiation plate 115.

As in the first preferred embodiment, since the loop surface of thecoupling electrode 135 is arranged so as to be perpendicular orsubstantially perpendicular to the radiation plate 115, the wireless ICdevice component functions as the wireless IC device even if thewireless IC device component is arranged on the metal surface.

Third Preferred Embodiment

A wireless IC device component according to a third preferred embodimentof the present invention preferably includes a coupling electrode 145having a U-shape in a side view, as shown in FIG. 4. The couplingelectrode 145 is preferably provided from the front surface of a base(not shown) made of resin, for example, to the rear surface thereof andincludes an opening 147 and a slit 148 extending to the opening 147 onits surface. The opening 147 and the slit 148 define a pair of couplingportions 146 a and 146 b to be coupled to the wireless IC chip 5. Thecoupling electrode 145 includes opposing ends 146 c and 146 d. Theopposing ends 146 c and 146 d are capacitively coupled to each other.

The opposing end 146 c is capacitively coupled to the opposing end 146d, so that the coupling electrode 145 electrically forms an annularelectrode, functions as a magnetic-field antenna, and is coupled to theradiation plate 115. The operational effects of the third preferredembodiment are similar to those of the second preferred embodiment.

The difference in voltage between the opposing ends 146 c and 146 d isrelatively large in the coupling electrode 145 of the third preferredembodiment, such that the opposing end 146 c can be capacitively coupledto the opposing end 146 d even if the opposing end 146 c is a certaindistance apart from the opposing end 146 d.

Fourth Preferred Embodiment

A wireless IC device according to a fourth preferred embodiment of thepresent invention preferably includes the wireless IC chip 5 arranged toprocess transmission and reception signals having certain frequencies, aradiation plate 15 provided on a base 10, such as a PET film, forexample, and a coupling electrode 25 provided on a base 20, such as aPET film, for example, as shown in FIGS. 5A and 5B.

The coupling electrode 25 preferably includes a pair of couplingportions 26 a and 26 b arranged to be coupled to the wireless IC chip 5and a pair of opposing ends 26 c and 26 d defined by a cutout of thecoupling electrode 25. The wireless IC chip 5 preferably includes, forexample, a clock circuit, a logic circuit, and a memory circuit.Necessary information is stored in the wireless IC chip 5. A pair ofinput-output terminal electrodes (not shown) is provided on the rearsurface of the wireless IC chip 5. The pair of input-output terminalelectrodes is mounted on the pair of coupling portions 26 a and 26 b ofthe coupling electrode 25 via a conductive adhesive 6 in a manner shownin FIG. 6.

The radiation plate 15 preferably has a dipole shape extending towardboth ends in a meandering pattern, for example, and includes amidsection 15 a of the radiation plate 15 is overlapped with theopposing ends 26 c and 26 d of the coupling electrode 25 to becapacitively coupled to the opposing ends 26 c and 26 d. The capacitivecoupling between the opposing ends 26 c and 26 d and the radiation plate15 causes the opposing ends 26 c and 26 d to be electrically connectedto each other via the radiation plate 15 and, thus, the couplingelectrode 25 defines an annular electrode. The radiation plate 15 andthe coupling electrode 25 are each preferably provided by attaching ametal thin film made of a conductive material, such as an aluminum foilor a copper foil, for example, on the bases 10 and 20 to form a pattern,applying a conductive paste made of, for example, Al, Cu, or Ag on thebases 10 and 20, or forming a pattern on a film provided by plating.

The coupling electrode 25 preferably has a certain length from thecoupling portions 26 a and 26 b to the opposing ends 26 c and 26 d, hasa certain resonant frequency corresponding to the electrical length, andalso functions as a matching portion arranged to perform the phasematching. The radiation plate 15 also has a certain resonant frequencycorresponding to the electrical length of the radiation plate 15. Inaddition, the coupling electrode 25 performs the impedance matchingbetween the wireless IC chip 5 and the radiation plate 15.

Accordingly, a transmission signal that is sent from the wireless ICchip 5 and that has a certain frequency is transmitted to the radiationplate 15 via the coupling electrode 25, and a signal having a certainfrequency is selected by the coupling electrode 25 from signals receivedby the radiation plate 15 and the selected signal is supplied to thewireless IC chip 5. Accordingly, in the wireless IC device, the wirelessIC chip 5 is operated with the signal received by the radiation plate 15and the response signal from the wireless IC chip 5 is externallyradiated from the radiation plate 15.

In the wireless IC device, the capacitive coupling between the couplingelectrode 25 and the radiation plate 15 causes the wireless IC chip 5 tobe coupled to the radiation plate 15 to establish the communicationbetween the wireless IC chip 5 and an RFID system in a non-contactmanner. Energy is transmitted between the coupling electrode 25 and theradiation plate 15 primarily through the magnetic coupling.

The coupling electrode 25 has an inductive reactance (XL: jωL) caused bythe electrical length and a capacitive reactance (XC: 1/jωC) caused bythe coupling electrode 25 and the radiation plate 15. Since theinductive reactance has a phase opposite to that of the capacitivereactance, the impedance does not significantly increase because of theincrease in the electrical length of the coupling electrode 25. In otherwords, it is possible to achieve the impedance matching between thewireless IC chip 5 and the radiation plate 15 even if the electricallength of the coupling electrode 25 is increased. The impedance matchingis preferably performed by setting a reactance between the wireless ICchip 5 and one terminal of the coupling electrode 25 and also setting areactance between the other terminal of the coupling electrode 25 andthe radiation plate 15 so as to have a complex conjugate relationship.

In other words, since the coupling electrode 25 is capacitively coupledto the radiation plate 15 to provide the capacitive reactance, it isnecessary for the coupling electrode 25 to have a relatively largerinductive reactance in order to achieve a certain impedance and theelectrical length of the coupling electrode 25 is increased. The longerelectrical length causes the coupling electrode 25 to receive anincreased amount of magnetic field from the radiation plate 15 and,thus, the magnetic coupling between the coupling electrode 25 and theradiation plate 15 is further strengthened.

In addition, since the coupling electrode 25 is capacitively coupled tothe radiation plate 15 via the opposing ends 26 c and 26 d, the mountingaccuracy of the coupling electrode 25 on the radiation plate 15 is notstrictly limited.

A portion of the signals from the coupling electrode is externallyradiated from the wireless IC device as the magnetic field and signalsare also externally radiated from the radiation plate 15 as the electricfield. Designing the coupling electrode 25 so as to have a resonantfrequency lower than the resonant frequency of the radiation plate 15enables the radiation characteristics to be broadened. The radiationplate 15 is capable of long-range communication by using the electricfield and the coupling electrode 25 is capable of short-rangecommunication by using the magnetic field.

In addition, since three sides of the coupling electrode 25 arepreferably arranged relatively close to the radiation plate 15 andsecondary electromagnetic coupling occurs at the proximity portion, thecoupling between the coupling electrode 25 and the radiation plate 15can be further strengthened. Consequently, it is possible to improve theradiation gain of the wireless IC device and to further broaden theradiation characteristics thereof.

As described above, since the resonant frequency of a signal is set inthe coupling electrode 25 in the wireless IC device, the wireless ICdevice operates properly even if the wireless IC device is mounted onvarious articles. Accordingly, variations in the radiationcharacteristics are prevented or minimized and it is not necessary tochange the design of, for example, the radiation plate 15 for eacharticle upon which the wireless IC device is to be mounted. Thefrequency of a transmission signal radiated from the radiation plate 15and the frequency of a reception signal to be supplied to the wirelessIC chip 5 substantially correspond to the resonant frequency of thecoupling electrode 25. Since the frequencies of transmission andreception signals are determined in the coupling electrode 25, thefrequency characteristics do not vary to achieve stable frequencycharacteristics, regardless of the shape, the size, and/or thearrangement relationship of the radiation plate 15, for example, even ifthe wireless IC device is rounded or is sandwiched between dielectricmaterials.

The shape of the radiation plate 15 is not limited to the dipole shapeand a radiation plate 65 having an increased area shown in a sixthpreferred embodiment of the present invention described below (refer toFIGS. 14 and 15) may be used. In this case, the base 20 is attached onthe radiation plate 65. The radiation plate 65 may be a portion of anarticle. In addition, the midsection 15 a of the radiation plate 15 maybe narrower or wider than the width shown in FIG. 5. Alternatively, thecoupling electrode 25 may be shifted leftward or rightward with respectto the central portion of the radiation plate 15.

The coupling electrode 25 may have various shapes including anelliptical or substantially elliptical shape, for example, instead ofthe rectangular or substantially rectangular shape in the fourthpreferred embodiment. For example, the coupling electrode 25 may be bentinto multiple portions, for example, as shown in FIG. 7. The sameapplies to other preferred embodiments of the present inventiondescribed herein.

Alternatively, the coupling electrode 25 may be arranged so as to beperpendicular or substantially perpendicular to the radiation plate 15,as shown in FIG. 8, and the pair of opposing ends 26 c and 26 d may becapacitively coupled to the radiation plate 15. The arrangement of theloop surface of the coupling electrode 25 so as to be perpendicular orsubstantially perpendicular to the radiation plate 15 in the abovemanner causes a magnetic field parallel or substantially parallel to theradiation plate 15 to be produced. Consequently, an electric fieldperpendicular or substantially perpendicular to the radiation plate 15is produced, a magnetic-field loop is induced by the electric-fieldloop, and this chain expands the electromagnetic-field distribution. Asa result, the wireless IC device is functional even if the wireless ICdevice is arranged on the metal surface. The opposing ends 26 c and 26 dof the coupling electrode 25 may be opposed to the metal surface to becapacitively coupled to the metal surface so as to cause the metalsurface to function as the radiation plate 15.

Fifth Preferred Embodiment

The wireless IC chip 5 may preferably be installed on a feed circuitboard 1, as shown in FIGS. 9A and 9B. An example in which the wirelessIC chip 5 is installed on the feed circuit board 1 is described as afifth preferred embodiment of the present invention. The radiation plate15 preferably including the meandering pattern described in the fourthpreferred embodiment or the radiation plate 65 having a larger areadescribed below in the sixth preferred embodiment, for example, maypreferably be used as the radiation plate, although not shown. Theopposing ends of the coupling electrode 25 are capacitively coupled tothe radiation plate 15 or 65.

The feed circuit board 1 preferably includes a feed circuit 11(described in detail below with reference to FIG. 12) including aresonant circuit and/or a matching circuit including inductance elementsL1 and L2 that have opposite phases and that are magnetically coupled toeach other (denoted by a mutual inductance M), as shown as an equivalentcircuit in FIG. 10.

In the wireless IC chip 5, input-output terminal electrodes arepreferably electrically connected to one end of a feed terminalelectrode 42 a provided on the feed circuit board 1 and to one end of afeed terminal electrode 42 b provided thereon, and mounting terminalelectrodes are preferably electrically connected to mounting electrodes43 a and 43 b via metallic bumps or other suitable structure, forexample, as shown in FIG. 11.

The inductance elements L1 and L2 included in the feed circuit 11 haveopposite phases and are magnetically coupled to each other to resonatewith the frequency processed by the wireless IC chip 5 and to beelectromagnetically coupled to the coupling portions 26 a and 26 b ofthe coupling electrode 25. The feed circuit 11 performs the impedancematching between the wireless IC chip 5 and the radiation plate 15.

Accordingly, preferably, the feed circuit 11 transmits a transmissionsignal that is sent from the wireless IC chip 5 and that has a certainfrequency to the radiation plate 15 via the coupling electrode 25, andthe feed circuit 11 selects a signal having a certain frequency fromsignals that are received by the radiation plate 15 and that aresupplied via the coupling electrode 25 and supplies the selected signalto the wireless IC chip 5. Accordingly, in the wireless IC device, thewireless IC chip 5 is operated with the signal received by the radiationplate 15 and the response signal from the wireless IC chip 5 isexternally radiated from the radiation plate 15. In other words, theresonant frequency of the feed circuit 11 substantially corresponds tothe frequency of a signal transmitted or received via the radiationplate 15.

The effects of the coupling electrode 25 are the same or substantiallythe same as those described in the fourth preferred embodiment, and theoperational effects of the fifth preferred embodiment are similar tothose of the fourth preferred embodiment.

The structure of the feed circuit board 1 will now be described withreference to FIG. 12. The feed circuit board 1 is preferablymanufactured by stacking, pressure-bonding, and firing ceramic sheets 41a to 41 h, each of which is made of a dielectric material or a magneticmaterial, for example. The top sheet 41 a includes the feed terminalelectrodes 42 a and 42 b, the mounting electrodes 43 a and 43 b,via-hole conductors 44 a, 44 b, 45 a, and 45 b provided thereon. Thesecond to eight sheets 41 b to 41 h each include line electrodes 46 aand 46 b provided thereon, which define the inductance elements L1 andL2. The second to eighth sheets 41 b to 41 h each include via-holeconductors 47 a, 47 b, 48 a, and 48 b, as required.

Stacking the sheets 41 a to 41 h provides the inductance element L1 inwhich the line electrodes 46 a are spirally connected via the via-holeconductor 47 a and provides the inductance element L2 in which the lineelectrodes 46 b are spirally connected via the via-hole conductor 47 b.A capacitance is produced between the line electrodes 46 a and 46 b.

An end 46 a-1 of the line electrode 46 a on the sheet 41 b is connectedto the feed terminal electrode 42 a via the via-hole conductor 45 a, andan end 46 a-2 of the line electrode 46 a on the sheet 41 h is connectedto the feed terminal electrode 42 b via the via-hole conductors 48 a and45 b. An end 46 b-1 of the line electrode 46 b on the sheet 41 b isconnected to the feed terminal electrode 42 b via the via-hole conductor44 b, and an end 46 b-2 of the line electrode 46 b on the sheet 41 h isconnected to the feed terminal electrode 42 a via the via-holeconductors 48 b and 44 a.

Since the inductance elements L1 and L2 are wound in opposite directionsin the feed circuit 11 described above, the magnetic field produced inthe inductance element L1 is offset by the magnetic field produced inthe inductance element L2. Since the magnetic fields are offset, it isnecessary for the line electrodes 46 a and 46 b to have an increasedlength in order to achieve a desired inductance value. Increasing thelength of the line electrodes 46 a and 46 b decreases the Q value so asto eliminate or reduce the steepness of the resonance characteristics,thus broadening the resonant characteristics near the resonantfrequency.

The inductance elements L1 and L2 are provided at different leftward andrightward positions in a perspective plan view of the feed circuit board1. The magnetic fields produced by the inductance elements L1 and L2have opposite directions. Accordingly, coupling the feed circuit to thecoupling portions 26 a and 26 b of the coupling electrode 25 causescurrents in opposite directions to be excited in the coupling portions26 a and 26 b to allow transmission and reception of signals to and fromthe radiation plate 15 via the coupling electrode 25.

In the fifth preferred embodiment using the feed circuit board 1, thecoupling electrode 25 may preferably be provided on the rear surface ofthe feed circuit board 1, as shown in FIG. 13. In this feed circuitboard 1, the coupling electrode 25 is arranged so as to be opposed tothe radiation plate 15 or the radiation plate 65 to capacitively couplethe opposing ends 26 c and 26 d to the radiation plate 15.Alternatively, the coupling electrode 25 may be arranged so as to beperpendicular or substantially perpendicular to the radiation plate 15or 65.

The feed circuit board 1 may preferably be a flexible board, forexample. The flexible board 1 may be used to attach the board 1 along acurved surface of an article. When the radiation plate 15 is provided asa portion of an article, it is possible to couple the coupling electrode25 without flexure even if the board 1 is attached along a curvedsurface of an article because the opposing ends 26 c and 26 d opposingthe radiation plate 15 are spaced apart from each other on one surfaceof the feed circuit board 1.

Sixth Preferred Embodiment

In a wireless IC device according to a sixth preferred embodiment of thepresent invention, a coupling electrode 55 is provided along surfaces ofa flexible dielectric substrate 50 preferably made of polyurethane, forexample, which is a wide band, as schematically shown in FIG. 14 and asshown in detail in FIG. 15. The wireless IC chip 5 (or the feed circuitboard 1 on which the wireless IC chip 5 is mounted) is preferablymounted on a pair of coupling portions 56 a and 56 b. A pair of opposingportions 56 c and 56 d oppose the broad radiation plate 65 provided onthe rear surface of a base 60 preferably made of a dielectric material,for example, to be capacitively coupled to the radiation plate 65. Thecapacitive coupling between the opposing ends 56 c and 56 d and theradiation plate 65 causes the opposing ends 56 c and 56 d to beelectrically connected to each other via the radiation plate 65 and,thus, the coupling electrode 55 defines an annular electrode. Asdescribed above in the first preferred embodiment, arranging the loopsurface of the coupling electrode 55 so as to be perpendicular orsubstantially perpendicular to the radiation plate 65 enables thewireless IC device to be arranged on the metal surface. The metalsurface may be caused to function as the radiation plate.

In the sixth preferred embodiment, the opposing ends 56 c and 56 d ofthe coupling electrode 55 oppose the radiation plate 65 via the base 60preferably made of a dielectric material, for example, to becapacitively coupled to the radiation plate 65. The operational effectsof the sixth preferred embodiment are the same or substantially the sameas the ones described in the first preferred embodiment. In the sixthpreferred embodiment, the base 60 and the radiation plate are notnecessarily defined by dedicated components of the wireless IC deviceand may be defined by portions of an article to which the dielectricsubstrate 50 of the coupling electrode 55 is attached. The radiationplate 65 may be, for example, a ground electrode of an electric deviceor an electronic device made of metal. In particular, since thedielectric substrate 50 is flexible and the coupling electrode 55 isseparated into left and right portions, the coupling electrode 55 can beeasily curved and, thus, can be attached along a curved surface of anarticle.

In the sixth preferred embodiment, the coupling electrode 55 maypreferably be incorporated into the feed circuit board 1 shown in thefifth preferred embodiment, along with the feed circuit 11, as shown inFIG. 16. Alternatively, the coupling electrode 55 may preferably beprovided on the rear surface of the feed circuit board 1. When thecoupling electrode 55 is incorporated into the feed circuit board 1, theopposing ends 56 c and 56 d of the coupling electrode 55 arecapacitively coupled to the radiation plate 65 via the dielectric layersof the board 1. Alternatively, the coupling electrode 55 may be adheredto the radiation plate 65 with a non-conductive adhesive, for example,to capacitively couple the coupling electrode 55 to the radiation plate65.

Seventh Preferred Embodiment

In a wireless IC device component according to a seventh preferredembodiment of the present invention, a coupling electrode 75 ispreferably provided along a flexible dielectric substrate (not shown)made of polyurethane, for example, which is a wide band, as shown inFIGS. 17A and 17B. The wireless IC chip 5 (or the feed circuit board onwhich the wireless IC chip 5 is mounted) is preferably mounted on a pairof coupling portions 76 a and 76 b. The coupling electrode 75 includes apair of opposing ends 76 c and 76 d. The opposing ends 76 c and 76 d areoverlapped with each other on the rear surface of a base to becapacitively coupled to each other.

The opposing end 76 c is capacitively coupled to the opposing end 76 d,so that the coupling electrode 75 electrically forms an annularelectrode and functions as a magnetic-field antenna. The wireless ICdevice component functions as a wireless IC device with the couplingelectrode 75 being coupled to the radiation plate. The operationaleffects of the seventh preferred embodiment are similar to those of thesecond preferred embodiment.

As described above in the first preferred embodiment, arranging the loopsurface of the coupling electrode 75 so as to be perpendicular orsubstantially perpendicular to the radiation plate enables the wirelessIC device to be arranged on the metal surface. The metal surface mayfunction as the radiation plate.

Eighth Preferred Embodiment

In a wireless IC device component according to an eighth preferredembodiment of the present invention, a coupling electrode 85 ispreferably provided along a flexible dielectric substrate 80 from thetop surface of the substrate 80 to the bottom surface thereof via leftand right end surfaces thereof, as shown in FIG. 18. The couplingelectrode 85 has a longitudinal direction and a latitudinal direction ina plan view, and a slit 87 having a flexion is provided at asubstantially central portion of the top surface. A pair of couplingportions 86 a and 86 b is preferably opposed to each other in thelatitudinal direction at a central portion of the slit 87, and the feedcircuit board 1 (refer to FIG. 11 and FIG. 12) on which the wireless ICchip 5 is mounted on the coupling portions 86 a and 86 b. The wirelessIC chip 5 is preferably sealed with a resin material 7, for example. Thewireless IC chip 5 may be directly mounted on the coupling portions 86 aand 86 b.

In the coupling electrode 85, preferably, a pair of opposing ends 86 cand 86 d is adjacent to a slit 88 at a central portion of the bottomsurface of the dielectric substrate 80. In the eighth preferredembodiment, the opposing end 86 c is capacitively coupled to theopposing end 86 d, so that the coupling electrode 85 electrically formsan annular electrode and functions as a magnetic-field antenna. Thewireless IC device component functions as a wireless IC device with thecoupling electrode 85 being coupled to the radiation plate. Theoperational effects of the eighth preferred embodiment are similar tothose of the seventh preferred embodiment.

In particular, the coupling electrode 85 includes the longitudinaldirection and the latitudinal direction in a plan view and the couplingportion 86 a opposes the coupling portion 86 b in the latitudinaldirection in the eighth preferred embodiment. Accordingly, even if thecoupling electrode 85 is flexed (the flexible dielectric substrate 80 islikely to be flexed in the longitudinal direction), it is possible toprevent the board 1 and the wireless IC chip 5 from being destroyed orseparated from one another due to the flexural stress applied to thefeed circuit board 1 and the wireless IC chip 5.

Ninth Preferred Embodiment

A wireless IC device component according to a ninth preferred embodimentof the present invention has the same or substantially the sameconfiguration as that of the eighth preferred embodiment, as shown inFIGS. 19A and 19B. The wireless IC device component of the ninthpreferred embodiment differs from the wireless IC device component ofthe eighth preferred embodiment in that the coupling portions 86 a and86 b are preferably arranged at positions different from those of thepair of opposing ends 86 c and 86 d in a plan view. The wireless IC chip5 may be directly mounted on the coupling portions 86 a and 86 b or thefeed circuit board 1 on which the wireless IC chip 5 is mounted may bemounted on the coupling portions 86 a and 86 b, as shown in the eighthpreferred embodiment.

The operational effects of the ninth preferred embodiment are similar tothose of the eighth preferred embodiment. Since the opposing ends 86 cand 86 d are defined by a cutout portion of the coupling electrode 85,the dielectric substrate 80 is likely to be bent at this cutout portion.In the ninth preferred embodiment, since the opposing ends 86 c and 86 dare arranged at positions different from those of the coupling portions86 a and 86 b in a plan view, the bending stress occurring at theopposing ends 86 c and 86 d is prevented from being transmitted to thecoupling portions 86 a and 86 b.

Accordingly, it is possible to suppress the effect of the bending stresson the wireless IC chip 5 and the feed circuit board 1 mounted on thecoupling portions 86 a and 86 b.

Tenth Preferred Embodiment

In a wireless IC device component of a tenth preferred embodiment, athrough hole 81 is preferably provided at a substantially centralportion of the dielectric substrate 80, the wireless IC chip 5 isdisposed in the hole 81, and the wireless IC chip 5 is coupled to thecoupling portions 86 a and 86 b bordering on the hole 81, as shown inFIG. 20. The feed circuit board 1 may be mounted in the couplingportions 86 a and 86 b in a state in which the feed circuit board 1 isdisposed in the hole 81.

The structure of the coupling electrode 85 in the tenth preferredembodiment is similar to the structure thereof in the ninth preferredembodiment. Accordingly, the operational effects of the tenth preferredembodiment are similar to those of the ninth preferred embodiment. Inparticular, in the tenth preferred embodiment, since the wireless ICchip 5 is incorporated in the dielectric substrate 80, it is possible toprotect the wireless IC chip 5 from an external impact and to reduce thesize of the wireless IC device component. In addition, since theopposing ends 86 c and 86 d are preferably arranged at positionsdifferent from those of the coupling portions 86 a and 86 b in a planview, the bottom face side of the hole 81 on which the coupling portions86 a and 86 b border is sealed with the coupling electrode 85. The holemay be a cavity (a housing portion) having a size sufficient to housethe wireless IC chip 5, instead of the through hole.

The wireless IC device component and the wireless IC device according tothe present invention are not limited to the preferred embodimentsdescribed above, and various changes and modifications may be made tothe present invention without departing from the spirit and scopethereof.

For example, the materials of the radiation plate and the base shown inthe above preferred embodiments are only examples, and the radiationplate and the base may be made of an arbitrary material as long as thematerial has necessary characteristics. Processing other than the metalbumping may be used to connect the wireless IC chip to the electrodes.

The wireless IC may be manufactured as an element in the feed circuitboard. The provision of the wireless IC in the feed circuit boardeliminates parasitic components in the portion in which the wireless ICis connected to the feed circuit to improve the characteristics of thewireless IC device. In addition, the height of the wireless IC devicecan be reduced. Furthermore, the shape and/or arrangement of the portionat which the feed circuit is coupled to the coupling electrode can bechanged to cause the feed circuit to be coupled to the couplingelectrode only through the electric field or the magnetic field. Thecoupling portions may not be defined by a pair of ends and may be linearportions as long as the wireless IC or the feed circuit can be coupledto the coupling portions. The pair of opposing ends of the couplingelectrode or the opposing ends opposing the radiation plate may becapacitively coupled to each other via another electrode.

As described above, preferred embodiments of the present invention areuseful for the wireless IC device components and the wireless IC devicesand, in particular, preferred embodiments of the present invention areexcellent in that the coupling electrode can be more satisfactorilycoupled to the radiation plate.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. A wireless IC device component comprising: a wireless IC; and acoupling electrode including at least one coupling portion arranged tobe coupled to the wireless IC directly or via a feed circuit and a pairof ends capacitively coupled to each other.
 2. The wireless IC devicecomponent according to claim 1, wherein the pair of ends in the couplingelectrode are opposed to each other so as to be capacitively coupled toeach other, thereby electrically forming an annular electrode.
 3. Thewireless IC device component according to claim 1, wherein the couplingelectrode includes a longitudinal direction and a latitudinal directionin a plan view and the coupling portions are opposed to each other inthe latitudinal direction.
 4. The wireless IC device component accordingto claim 1, wherein the coupling portions are arranged at positionsdifferent from those of the pair of ends in a plan view.
 5. The wirelessIC device component according to claim 1, wherein the coupling electrodeis provided on a first main surface of a dielectric substrate and thepair of opposing ends are provided on a second main surface of thedielectric substrate opposite to the first main surface of thedielectric substrate.
 6. A wireless IC device comprising: a wireless IC;a coupling electrode including at least one coupling portion arranged tobe coupled to the wireless IC directly or via a feed circuit and a pairof ends capacitively coupled to each other; and a radiation platecoupled to the coupling electrode.
 7. The wireless IC device accordingto claim 6, wherein the pair of ends in the coupling electrode areopposed to each other so as to be capacitively coupled to each other,thereby electrically forming an annular electrode.
 8. A wireless ICdevice comprising: a wireless IC; a coupling electrode including atleast one coupling portion to be coupled to the wireless IC directly orvia a feed circuit and a pair of opposing ends defined by a cutoutportion of the coupling electrode; and a radiation plate opposed to thepair of opposing ends in the coupling electrode so as to be capacitivelycoupled to the pair of opposing ends.
 9. The wireless IC deviceaccording to claim 8, wherein the pair of opposing ends in the couplingelectrode are capacitively coupled to the radiation plate toelectrically form an annular electrode.
 10. The wireless IC deviceaccording to claim 6, wherein the coupling electrode includes alongitudinal direction and a latitudinal direction in a plan view andthe coupling portions are opposed to each other in the latitudinaldirection.
 11. The wireless IC device according to claim 6, wherein thecoupling portions are arranged at positions different from those of thepair of ends in a plan view.
 12. The wireless IC device according toclaim 6, wherein the coupling electrode is provided on a first mainsurface of a dielectric substrate and the pair of ends are provided on asecond main surface of the dielectric substrate opposite to the firstmain surface of the dielectric substrate.
 13. The wireless IC deviceaccording to claim 6, wherein a loop surface of the coupling electrodeis arranged so as to be perpendicular or substantially perpendicular tothe radiation plate.
 14. The wireless IC device according to claim 6,wherein the wireless IC is mounted on or in a feed circuit board and thefeed circuit board includes at least one of a resonant circuit amatching circuit.
 15. The wireless IC device according to claim 14,wherein a resonant frequency of the resonant circuit substantiallycorresponds to a frequency of a signal transmitted or received via theradiation plate.
 16. The wireless IC device according to claim 14,wherein the coupling electrode is provided on or in the feed circuitboard.
 17. The wireless IC device according to claim 14, wherein thefeed circuit board is a flexible board.
 18. The wireless IC deviceaccording to claim 6, wherein the radiation plate is defined by aportion of an article.